The present invention relates generally to composites and, more particularly, to polymer and inorganic-organic hybrid composites containing inorganic or organic materials disposed in the polymer matrix""s free volume
Hybrid Materials
Inorganic-organic hybrid materials have been used with varying degrees of success for a variety of applications.
In some of these materials, organic polymers are blended with inorganic fillers to improve certain properties of those polymers or to reduce the cost of the polymeric compositions by substituting cheaper inorganic materials for more expensive organic materials. Typically, inorganic fillers are either particulate or fibrous and are derived from inexpensive materials, such as naturally occurring minerals and glass. For example, U.S. Pat. No. 5,536,583 to Roberts et al. (xe2x80x9cRobertsxe2x80x9d) describes methods for mixing inorganic ceramic powders into polyethersulfone, polyether ketones, and polyether other ketones and methods for including metal nitrides, oxides, and carbides into fluoropolymer resins to produce corrosion inhibiting coatings as well as coatings which have improved abrasion resistance and/or enhanced bonding characteristics. U.S. Pat. No. 5,492,769 to Pryor et al. (xe2x80x9cPryorxe2x80x9d) describes methods for embedding metal or ceramic materials into organic polymeric materials to increase the polymer""s abrasion resistance. U.S. Pat. No. 5,478,878 to Nagaoka et al. (xe2x80x9cNagaokaxe2x80x9d) describes a thermoplastic blend of an organic polymer and inorganic metallic fillers which improves the polymer""s resistance to discoloration upon exposure to ambient light sources.
Each of the above inorganic-organic hybrid materials were made either (1) by melting and then mixing the inorganic and organic phases into a homogeneous mixture which was then cured, extracted, or dried or (2) by dissolving the polymer and inorganic material together in a solvent in which both materials were miscible, mixing to produce a homogeneous solution, and then evaporating the solvent to extract the hybrid material. The resulting inorganic-organic hybrid materials are essentially homogeneous macromolecular blends which have separate inorganic and organic domains which range from nanometers to tens of micrometers in size. All of the above composites are fabricated by using inorganic materials, typically naturally occurring minerals, which are in thermodynamically stable metallic forms, such as metal oxides, metal nitrides, and zero-valent metals.
These inorganic-organic hybrid materials suffer from a number of drawbacks which limit their utility. For example, the size of the domain that the inorganic materials assume within the hybrid depends on the particle size of the inorganic material particulate or fiber used in making the hybrid. In addition, the homogeneity of the inorganic-organic hybrid material largely depends on either the solubility of the inorganic material in the polymeric melt or on the solubility of the inorganic material in the solvent used to solubilize the polymeric material. Furthermore, the properties and molecular structures of these hybrids depend greatly on the methods used to extrude, cast, or dry the solid hybrid material from the melt or solubilized mixtures, which gives rise to significant, undesirable, and frequently uncontrollable batch-to-batch and regional variations.
Inorganic-organic hybrid materials have also been prepared by dispersing powdered or particulate forms of inorganic materials within various polymeric matrices.
For example, U.S. Pat. No. 5,500,759 to Coleman (xe2x80x9cColemanxe2x80x9d) discloses electrochromic materials made by dispersing electrically conductive metal particles into polymeric matrices; U.S. Pat. No. 5,468,498 to Morrison et al. (xe2x80x9cMorrisonxe2x80x9d) describes aqueous-based mixtures of colloidal vanadium oxide and dispersed sulfonated polymer which are useful for producing antistatic polymeric coatings; U.S. Pat. No. 5,334,292 to Rajeshwar et al. (xe2x80x9cRajeshwarxe2x80x9d) discloses conducting polymer films containing nanodispersed inorganic catalyst particles; and U.S. Pat. No. 5,548,125 to Sandbank (xe2x80x9cSandbankxe2x80x9d) discloses methods for melt- or thermo-forming flexible polymeric gloves containing particulate tungsten which makes the gloves useful for shielding x-radiation.
Although the inorganic-organic hybrid materials are homogeneously mixed, they contain separate inorganic and organic phases on a macromolecular scale. These separate phases frequently gives rise to the inorganic material""s migration within and/or leaching out of the polymeric matrix. Furthermore, the inorganic phases of these inorganic-organic hybrid materials can be separated from the polymer matrix by simple mechanical processes or by solvent extraction of the polymer. Consequently, upon exposure to certain temperatures or solvents, the inorganic phases of these hybrids can migrate and dissipate out of or accumulate in various regions within the polymeric matrix, reducing its useful life.
Because of the problems associated with migration and leaching of the inorganic phase in inorganic-organic hybrids, hybrid materials containing inorganic phases having greater stability have been developed. These materials rely on physically entrapping large interpenetrating macromolecular networks of inorganic materials in the polymeric chains of the organic material.
For example, U.S. Pat. No. 5,412,016 to Sharp (xe2x80x9cSharpxe2x80x9d) describes polymeric inorganic-organic interpenetrating network compositions made by mixing a hydrolyzable precursor of an inorganic gel of Si, Ti, or Zr with an organic polymer and an organic carboxylic acid to form a homogeneous solution. The solution is then hydrolyzed, and the resulting hybrid materials are used to impart added toughness to conventional organic polymers as well as to increase their thermal stabilities and abrasion resistances. U.S. Pat. No. 5,380,584 to Anderson et al. (xe2x80x9cAnderson Ixe2x80x9d) describes an electrostatography imaging element which contains an electrically-conductive layer made of a colloidal gel of vanadium pentoxide dispersed in a polymeric binder. U.S. Pat. No. 5,190,698 to Coltrain et al. (xe2x80x9cColtrain Ixe2x80x9d) describes methods for making polymer/inorganic oxide composites by combining a polymer derived from a vinyl carboxylic acid with a metal oxide in a solvent solution, casting or coating the resulting solution, and curing the resulting sample to form a composite of the polymer and the metal oxide. These composites are said to be useful for forming clear coatings or films having high optical density, abrasion resistance, or antistatic properties. U.S. Pat. No. 5,115,023 to Basil et al. (xe2x80x9cBasilxe2x80x9d) describes siloxane-organic hybrid polymers which are made by hydrolytic condensation polymerization of organoalkyoxysilanes in the presence of organic film-forming polymers. The method is similar to that described in Sharp and, similarly, is used to improve a polymer""s mechanical strength and stability while maintaining its flexibility and film forming properties. U.S. Pat. No. 5,010,128 to Coltrain et al. (xe2x80x9cColtrain IIxe2x80x9d) describes methods for blending metal oxides with etheric polyphosphazenes to increase abrasion resistance and antistatic properties of polyphosphazene films. These methods, like those of Coltrain I, employ inorganic metal precursors which contain hydrolyzable leaving groups.
In each of the foregoing, the polymeric inorganic-organic interpenetrating network compositions are obtained by, sequentially, (1) adding hydrolyzable metals (or hydrolyzed metal gels) into either a polymer melt or a solvent containing a dissolved polymer; (2) adding a hydrolyzing agent or adjusting the pH of the solution to effect hydrolysis; (3) mixing; and (4) curing.
The methods described, however, suffer from several limitations. For example, they are limited to incorporating interpenetrating metal oxide networks into polymers which have similar solubilities as the hydrolyzable metal precursors or the hydrolyzed metal. In addition, because the method involves first mixing the inorganic hydrolyzable metal precursors or the hydrolyzed metal with the organic polymer and then curing the mixture, curing of the inorganic phase and organic phase necessarily occurs simultaneously. Since both the inorganic and organic materials are in intimate contact during the curing process, the organic phase of the resulting hybrid has physical characteristics different from that of the same polymer cured in the absence of an inorganic phase. This makes it difficult and, in many cases, impossible to predict the concentration of inorganic material necessary to preserve the desired properties of the starting organic polymer material or to predict the properties of the resulting hybrid. Typically, crystallinity and/or free volume in the hybrid materials are significantly different than the starting organic polymer materials cured in the absence of the inorganic phase. The methods also have limited utility because they provide no control over the spatial distribution of the inorganic and organic phases within the polymeric inorganic-organic interpenetrating network hybrid. For example, it is difficult and, in many cases, impossible to control which phase dominates the surface of the bulk material or the surface of the free volume within the bulk material. This variability can cause quality control problems as well as limit the usefulness of the hybrid materials.
Alternatively, it has been demonstrated that inorganic and organic molecules can be impregnated into solid matrices using supercritical fluids.
WO 94/18264 to Perman et al. describes the use of supercritical fluids for impregnating a variety of specific additives into polymer substrates by simultaneously contacting the polymer substrate with the impregnation additive and a carrier liquid, such as water, in the presence of a supercritical fluid. The described method requires that a polymeric material be simultaneously exposed to an impregnation additive and a carrier liquid, and, then, all three of these components are exposed to a supercritical fluid in a high pressure vessel for a sufficient time to swell the polymeric material so that the carrier liquid and impregnation additive can penetrate the swollen polymeric material.
In Clarke et al., J. Am. Chem. Soc., 116:8621 (1994), supercritical fluid is used to impregnate polyethylene with CpMn(CO)3 using supercritical CO2 which acts to both solvate the CpMn(CO)3 and to swell the polyethylene, thus permitting the flow of CpMn(CO)3 into the free space created in the swollen polymer and into the free volume of the polymeric material.
Watkins et al., Macromolecules, 28:4067 (1995) discloses methods for polymerizing styrene in supercritical CO2-swollen poly(chlorotrifluoroethylene) (xe2x80x9cPCTFExe2x80x9d).
Methods for impregnating polymeric materials with additives using supercritical fluids suffer from a number of important drawbacks. First, the method requires the use of a high pressure apparatus. Second, the method requires that the supercritical fluid or another suitable carrier solvent be available to solvate the additive to be impregnated in the polymer matrix. Third, the method requires that the polymeric material be grossly swollen to permit the additive to penetrate and, thus, to impregnate the polymeric material. This swelling results in large changes in the host polymer""s surface and bulk morphology and also results in a lack of control of the final hybrid material""s composition. Together, these changes and lack of control lead to a variety of physical and chemical changes in the host polymer, including changes in properties such as flexibility, crystallinity, and thermal characteristics. Finally, in most cases where supercritical methods are used to impregnate additives into polymeric materials, the impregnated additive can be readily diffused out of the polymeric material by exposure of the polymeric material to supercritical fluid conditions or, in some cases, to various solvents.
For these and other reasons, there remains a need for inorganic-organic polymer composites and for methods of preparing these inorganic-organic polymer composites which do not suffer from the above-described limitations. The present invention is directed to meeting this need.
The present invention relates to a composite. The composite includes a polymer matrix having a natural free volume therein and an inorganic or organic material disposed in the natural free volume of the polymer matrix.
The present invention also relates to a method for making a composite. A polymer matrix having free volume therein is provided. The free volume of the polymer matrix is evacuated, and inorganic or organic molecules are infused into the evacuated free volume of the polymer matrix. In a particularly preferred embodiment of the present invention, the inorganic or organic molecules are then polymerized under conditions effective to assemble the inorganic or organic molecules into macromolecular networks.
The present invention also relates to a composite which includes a polymer matrix having natural free volume therein and an inorganic or organic material disposed in the natural free volume of the polymer matrix. The polymer matrix is at least partially amorphous and includes a functionality. The inorganic or organic material includes a first functional group which is interacted with the polymer matrix""s functionality and a second functional group which is not interacted with the polymer matrix""s functionality.
The present invention also relates to a method for making a composite. The method includes providing a polymer matrix which has free volume therein, which is at least partially amorphous, and which includes a functionality. The free volume of the polymer matrix is evacuated, and inorganic or organic molecules are infused into the evacuated free volume of the polymer matrix. The inorganic or organic molecules include a first functional group which is capable of interacting with the polymer matrix""s functionality and a second functional group which is either capable or not capable of interacting with the polymer matrix""s functionality. The method further includes treating the inorganic or organic molecules under conditions effective to cause the inorganic or organic molecules"" first functional group to interact with the polymer matrix""s functionality but not effective to cause the organic molecules"" second functional group to interact with the polymer matrix""s functionality.
The present invention further relates to a composite which includes a polymer matrix having free volume therein and an inorganic material disposed in the polymer matrix""s free volume. In this composite, the polymer matrix is at least partially amorphous, and the inorganic material comprises vanadium and titanium.
The present invention also relates to a composite which includes a polymer matrix having free volume therein and an inorganic or organic material disposed in the polymer matrix""s free volume. The inorganic or organic material is a macromolecular network having the formula [xe2x80x94Si(R1)(R2)xe2x80x94Oxe2x80x94]m, where R1 is an alkyl group or an aryl group, R2 is an alkyl group or an aryl group, and m is an integer from 2 to about 10,000.
The present invention further relates to a method for making a composite. The method includes providing a polymer matrix having free volume therein, the polymer matrix being at least partially amorphous. The free volume of the polymer matrix is evacuated, and inorganic or organic molecules are infused into the polymer matrix""s evacuated free volume. In this method, the inorganic or organic molecules have a formula selected from the group consisting of Si(R1)(X)3 and Si(R1)(R2)(X)2 where R1 and R2 are independently selected from an alkyl group or aryl group and each X is, independently, a halogen or an alkoxy group.
The composites of the present invention contain polymeric phases which have physical properties substantially similar to the properties of the native polymer matrix (i.e., polymer matrix in the absence of inorganic or organic molecules or macromolecular networks). Consequently, the composites of the present invention, relative to conventional inorganic-organic hybrid materials, have significantly more predictable mechanical properties. The composites of the present invention also have controllable, predictable, and reproducible levels of optical densities and electrical, ionic, and charged species conductivities, which make them useful in various applications including photoradiation shields and filters, electromagnetic radiation shields and filters, heterogeneous catalytic substrates, and conducting electrodes. These characteristics also make these composites useful as components in the construction of electrolytic cells, fuel cells, optoelectronic devices, and materials having flame and heat retardant properties.
Although the initial formation of these composites results in materials having physical properties substantially similar to those of the native polymeric matrix, subsequent thermal, chemical, photochemical, or electrochemical treatment of the composites produced in accordance with the present invention can lead to improved physical properties. It is believed that these changes in the physical properties of the composite result from chemical and/or electronic interactions between the infused inorganic or organic molecules and the polymer matrix.
The present invention relates to a composite. The polymer composite includes a polymer matrix which has natural free volume therein and an inorganic or organic material disposed in the natural free volume of the polymer matrix.
The polymer matrix can be an organic based polymer or an inorganic-organic hybrid polymer. Organic based polymers suitable for use in the composites of the present invention can be homopolymers, copolymers, multicomponent polymers, or combinations thereof. Suitable organic polymers include halopolymers, such as fluoropolymers and fluorochloropolymers, polyimides, polyamides, polyalkylenes, such as polyethylene, polypropylene, and polybutylenc, poly(phenylenediamine terephthalamide) filaments, modified cellulose derivatives, starch, polyesters, polymethacrylates, polyacrylates, polyvinyl alcohol, copolymers of vinyl alcohol with ethylenically unsaturated monomers, polyvinyl acetate, poly(alkylene oxides), vinyl chloride homopolymers and copolymers, terpolymers of ethylene with carbon monoxide and with an acrylic acid ester or vinyl monomer, polysiloxanes, polyfluoroalkylenes, poly(fluoroalkyl vinyl ethers), homopolymers and copolymers of halodioxoles and substituted dioxoles, polyvinylpyrrolidone, or combinations thereof. Halopolymers are organic polymers which contain halogenated groups, such as fluoroalkyl, difluoroalkyl, trifluoroalkyl, fluoroaryl, difluoroalkyl, trifluoroalkyl, perfluoroalkyl, perfluoroaryl chloroalkyl, dichloroalkyl, trichloroalkyl, chloroaryl, dichloroalkyl, trichloroalkyl, perchloroalkyl, perchloroaryl, chlorofluoroalkyl, chlorofluoroaryl, chlorodifluoroalkyl, and dichlorofluoroalkyl groups. Halopolymers include fluorohydrocarbon polymers, such as polyvinylidine fluoride (xe2x80x9cPVDFxe2x80x9d), polyvinylflouride (xe2x80x9cPVFxe2x80x9d), polychlorotetrafluoroethylene (xe2x80x9cPCTFExe2x80x9d), polytetrafluoroethylene (xe2x80x9cPTFExe2x80x9d) (including expanded PTFE (xe2x80x9cePTFExe2x80x9d). Fluoropolymers are preferred for many applications because of their extreme inertness, high thermal stability, hydrophobicity, low coefficients of friction, and low dielectric properties. In addition to retaining these desirable properties, in many applications, particularly catalytic applications, it is advantageous to utilize the highly electronegative characteristics of these fluoropolymers for enhancing the catalytic properties of metals by associating these metals with the fluoropolymers. Suitable fluoropolymers include perfluorinated resins, such as perfluorinated siloxanes, perfluorinated styrenes, perfluorinated urethanes, and copolymers containing tetrafluoroethylene and other perfluorinated oxygen-containing polymers like perfluoro-2,2-dimethyl-1,3-dioxide (which is sold under the trade name TEFLON-AF). Other polymers which can be used in the composites of the present invention include perfluoroalkoxy-substituted fluoropolymers, such as MFA (available from Ausimont USA (Thoroughfare, N.J.)) or PFA (available from Dupont (Willmington, Del.)), polytetrafluoroethylene-co-hexafluoropropylene (xe2x80x9cFEPxe2x80x9d), ethylenechlorotrifluoroethylene copolymer (xe2x80x9cECTFExe2x80x9d), and polyester based polymers, examples of which include polyethyleneterphthalates, polycarbonates, and analogs and copolymers thereof.
Polyphenylene ethers can also be employed. These include poly (2,6-dimethyl-1,4-phenylene ether), poly(2,6-diethyl-1,4-phenylene ether), poly(2-methyl-6-ethyl-1,4-phenylene ether), poly(2-methyl-6-propyl-1,4-phenylene ether), poly(2,6-dipropyl-1,4-phenylene ether), poly(2-ethyl-6-propyl-1,4-phenylene ether), poly(2,6-dibutyl-1,4-pheneylene ether), and the like.
Examples of suitable polyamides include polyhexamethylene alipamide (nylon 66), polyhexamethylene azelamide (nylon 69), polyhexamethylene sebacamide (nylon 610), polyhexamethylene dodecanoamide (nylon 612), poly-bis-(p-aminocyclohexyl) methane dodecanoamide, polytetramethylene alipamide (nylon 46) and polyamides produced by ring cleavage of a lactam such as polycaprolactam (nylon 6) and polylauryl lactam. Furthermore, there may be used polyamides produced by polymerization of at least two amines or acids used for the production of the above-mentioned polymers, for example, polymers produced from adipic acid, sebacic acid and hexamethylenediamine. The polyamides further include blends of polyamides such as a blend of nylon 66 and nylon 6 including copolymers such as nylon 66/6.
Aromatic polyamides may also be used in the present invention. Preferably they are incorporated in copolyamides which contain an aromatic component, such as melt-polymerizable polyamides containing, as a main component, an aromatic amino acid and/or an aromatic dicarboxylic acid such as para-aminoethylbenzoic acid, terephthalic acid, and isophthalic acid.
Typical examples of the thermoplastic aromatic copolyamides include copolymer polyamide of p-aminomethylbenzoic acid and xcex5-caprolactam (nylon AMBA/6), polyamides mainly composed of 2,2,4-/2,4,4-trimethylhexamethylene-diamineterephthalamide (nylon TMDT and Nylon TMDT/61), polyamide mainly composed of hexamethylene diamineisophthalamide, and/or hexamethylenediamnineterephthalamide and containing, as another component, bis(p-aminocyclohexyl)methaneisophthalamide and/or bis(p-aminocyclohexyl)methaneterephthalamide, bis(p-aminocyclohexyl)propaneisophthalamide and/or bis(p-aminocyclohexyl)propaneterephthalamide, (nylon 6I/PACM I, nylon 6I/DMPACM I, nylon 6I/PACP I, nylon 6I/6T/PACM I/PACM T, nylon 6I/6T/DMPACM I/DMPACM T, and/or nylon 6I/6T/PACP I/PACP T).
Styrene polymers can also be used. These include polystyrene, rubber modified polystyrene, styrene/acrylonitrile copolymer, styrene/methylmethacrylate copolymer, ABS resin, styrene/alphamethyl styrene copolymer, and the like.
Other suitable representative polymers include, for example, poly(hexamethylene alipamide), poly(xcex5-caprolactam), poly(hexamethylene phthalamide or isophthalamide), poly(ethylene terephthalate), poly(butylene terephthalate), ethylcellulose and methylcellulose, poly(vinyl alcohol), ethylene/vinyl alcohol copolymers, tetrafluoroethylene/vinyl alcohol copolymers, poly(vinyl acetate), partially hydrolyzed poly(vinyl acetate), poly(methyl methacrylate), poly(ethyl methacrylate), poly(ethyl acrylate), poly(methyl acrylate), ethylene/carbon monoxide/vinyl acetate terpolymers, ethylene/carbon monoxide/methyl methacrylate terpolymers, ethylene/carbon monoxide/n-butyl acrylate terpolymers, poly(dimethylsiloxane), poly(phenylmethylsiloxane), polyphosphazenes and their analogs, poly(heptafluoropropyl vinyl ether), homopolymers and copolymers of perfluoro(1,3-dioxole) and of perfluoro(2,2-dimethyl-1,3-dioxole), especially with tetrafluoroethylene and optionally with another ethylenically unsaturated comonomer, poly(ethylene oxide), poly(propylene oxide), and poly(tetramethylene oxide).
These and other suitable polymers can be purchased commercially. For example, poly(phenylenediamine terephthalamide) filaments can be purchased from Dupont under the tradename KEVLAR(trademark). Alternatively, polymers suitable for the practice of the present invention can be prepared by well known methods, such as those described in Elias, Macromoleculesxe2x80x94Structure and Properties I and II, New York:Plenum Press (1977) (xe2x80x9cEliasxe2x80x9d), which is hereby incorporated by reference.
The polymer matrix can, alternatively, be an inorganic-organic hybrid polymer or blend of organic polymer and inorganic-organic hybrid polymer. Inorganic-organic hybrid polymers suitable for the practice of the present invention include those prepared by conventional methods for making organic-inorganic hybrid materials, such as those described in Roberts, Pryor, Nagaoka, Coleman, Morrison, Rajeshwar, Sandbank, Sharp, Anderson I, Basil, and Coltrain I and II, which are hereby incorporated by reference.
The polymer matrix, in addition to an organic based polymer or an inorganicorganic hybrid polymer, can contain a variety of materials which are known in the art to modify the properties of the polymer matrix. These include, fillers, cross-linking agents, stabilizers, radical scavengers, compatabilizers, antistatic agents, dyes, and pigments. Their inclusion or exclusion will depend, of course, on the use to which the composite will be put, as will be apparent to one skilled in the art.
The materials which make up the polymer matrix, be they an organic polymer or an inorganic-organic hybrid material, contain natural free volume.
The polymer matrix can be of any form suitable for the use to which the composite is to be put. For example, the polymer matrix can be an organic based polymer resin, powder, or particulate or, alternatively, an inorganic-organic hybrid polymer resin, powder, or particulate. Suitable particulate forms include sheets, fibers, or beads. As used herein, sheets are meant to include films, fibers are meant to include filaments, and beads are meant to include pellets. Beads having diameters of from about 0.1 mm to about 0.5 mm and powders having diameters of from about 10 nm to about 0.1 mm and made from PVDF, PTFE, FEP, ECTFE, PFA, or MFA are particularly useful in many applications.
Alternatively, the polymer matrix can be of a form that is different from the one desired for the composite. The inorganic or organic materials are infused into resins in the form of polymer powders, beads, or the like. The infused polymer powders, beads, etc. can then be processed by conventional polymer processing methods into the desired shape. For example, the infused polymer powders, beads, etc. can be extruded into finished sheets or fibers. Alternatively, the infused polymer powders, beads, etc. can be applied to solid objects, such as walls and boat hulls by, for example, spraying, sputtering, or painting (e.g., brushing or rolling) the infused polymer powders, beads, or pellets onto the object under conditions effective to produce a thin film or coating of the infused polymer on the object.
The composites of the present invention, particularly those in the form of beads, sheets, or fibers, can be infused uniformly or non-uniformly. For example, the present invention includes a sheet having two opposing surfaces where the portion of the sheet in proximity to one surface is infused while another portion of the sheet in proximity to the opposite surface is not. This non-uniform infusing can be carried out, for example, by covering one of the sheet""s surfaces with a material that prevents evacuation of the free volume in proximity to the covered surface or, alternatively or additionally, that prevents the infusing material from contacting the covered surface.
For purposes of this invention, free volume is used in a manner consistent with the description of free volume in Elias at pp. 186-188, which is hereby incorporated by reference. Briefly, Elias points out that, by definition, no extensive long-range order can exist in amorphous regions. Elias further notes that these amorphous regions are not x-ray crystalline, and, although studies suggest that x-ray amorphous polymers may have certain order, a definite number of vacant sites must be present. Thus, free volume, as used herein, relates to the vacant sites which are present in amorphous regions of a polymer matrix and into which organic or inorganic molecules can diffuse. The free volume is exploited in accordance with the present invention as regions into which inorganic or organic materials can be introduced, such as by diffusion, and subsequently assembled into macromolecular networks or stabilized through interaction with the polymer matrix""s functionality. These free volumes generally form during the curing process, such as upon evaporation of the solvent in which the polymer was formed, but the present invention is not intended to be limited by the mechanism by which the free volume comes to exist in the polymer matrix.
For purposes of this invention, free volumes can be natural free volumes or created free volumes. Natural free volumes, as used herein, relates to the vacant sites which are characteristically present in amorphous regions of a polymer matrix and into which organic or inorganic molecules can diffuse. These natural free volumes include those which are formed during the curing process, such as upon evaporation of the solvent in which the polymer was formed. In contrast, created free volumes are those free volumes which are produced or modified subsequent to the formation of the polymer matrix by exposing the polymer matrix to supercritical fluids under supercritical conditions. Since the free volumes of the composites of the present invention are natural free volumes and do not contain created free volumes, these natural free volumes contain substantially no carrier liquid or other solvent used in supercritical infusion processes.
The total natural free volume available for diffusing inorganic or organic molecules in a particular polymer matrix is dependent on a variety of characteristics of the natural free volume. These include the size, size distribution, concentration, and spatial distribution of the natural free volume, all of which are effected by the conditions under which the polymer matrix was formed, including, for example: how the solvent was removed; the pressure and temperature (and variations therein) during the solvent removal process; the degree to which the polymer was cured prior to onset of the solvent removal process; the nature of the solvent; the nature of the organic or inorganic-organic hybrid polymer; the size of the matrix; and the like. Another factor affecting the natural free volume of the polymer matrix is the degree of crystallinity. Polycrystalline regions contained within polymer matrix have less natural free volume than amorphous regions, are tightly packed, and inhibit movement of inorganic molecules into the polymer matrix. Thus, it is preferred that the polymer matrix have at least some degree of non-crystallinity (i.e., that it have a crystallinity of less than 100%). Suitable polymer matrices are those which have crystallinities of less than 99%, preferably less than 95%. The total natural free volume of the polymer matrix (i.e., the collective volume of the natural free volumes) (xe2x80x9cVsxe2x80x9d) is preferably greater that about 1xc3x9710xe2x88x926 of the total volume of the polymer matrix. Expressed differently, if the total volume of the polymer matrix is designated Vc, then the collective volume of the natural free volume is preferably greater than about 1xc3x9710xe2x88x926 Vc, more preferably from about 1xc3x9710xe2x88x926 Vc to about 0.1 Vc, and still more preferably from about 1xc3x9710xe2x88x923 Vc to about 0.1 Vc.
The natural free volume can be an inherent property of the polymer matrix (i.e., a property which is established by the method used to initially form the polymer matrix) or, alternatively, it can be controlled after formation of the polymer matrix by any suitable means (other than by exposure to supercritical fluids under supercritical conditions), such as by increasing or decreasing the temperature of the polymer matrix when the inorganic or organic materials are diffused thereinto. For example, increasing the temperature at which the inorganic or organic molecules are diffused into the polymer matrix increases the natural free volume of the polymer matrix without substantially altering its physical and mechanical properties. Thus, a greater concentration of the inorganic or organic molecules can be diffused into the polymer matrix, which results in, for example, a greater concentration of the macromolecular network in the polymer matrix.
Methods for determining the natural free volume as a fraction of the total polymer matrix volume (i.e., Vs/Vc) are well known to those skilled in the art. Illustrative methods can be found in Elias at pp. 256-259, which is hereby incorporated by reference. The polymer matrix""s natural free volume can also be determined by the flow rate of gases through the polymer matrix. Natural free volume and its distribution in the polymer matrix can also be determined by using a photoreactive probe, such as the one described in Horne, xe2x80x9cDynamics of Electron-Lattice Interactions,xe2x80x9d in Tsuchida, ed., Macromolecular Complexes: Dynamic Interactions and Electronic Processes, New York:VCH Publishers, pp. 39-59 (1991), which is hereby incorporated by reference.
As indicated above, the composite of the present invention further includes an inorganic or organic material which is disposed in the polymer matrix""s natural free volume. The amount of the inorganic or organic material within the natural free volume is typically proportionate to the internal surface area of the starting polymer matrix""s natural free volume, which, as described above, can be an inherent characteristic of the polymer matrix or can be controlled by any suitable means (other than by exposure to supercritical conditions), for example, by increasing or decreasing the temperature at which the inorganic or organic material is diffused thereinto. The inorganic material can fill the polymer matrix""s natural free volume or occupy a significant portion thereof in two or three dimensions. The inorganic material can itself form three dimensional networks within the polymer matrix""s natural free volume. These three dimensional networks can be dense, substantially filling all the natural free volume, or they can be porous, thus permitting the flow of gas molecules into and out of the natural free volume and through the three dimensional inorganic or organic macromolecular network. Alternatively, the inorganic material can be a two-dimensional layer (such as a coating or film) on or along the surface or a portion of the surface of the natural free volume. In the case where the natural free volume is small, the inorganic or organic material may follow the one-dimensional template of the starting material. This results in a two-dimensional morphology depending on the inherent chemistry and/or the physical morphology at the natural free-volume/polymer matrix interfaces. Preferably, the inorganic or organic material is homogeneously or substantially homogeneously spread throughout the entire natural free volume of the polymer matrix.
Any suitable inorganic material can be employed. Preferred inorganic materials suitable for use in the practice of the present invention are those capable of having a vapor pressure greater than zero at a temperature between room temperature and the thermal decomposition temperature of the polymeric matrix material and/or at pressures of from about 0.1 mTorr to about 10 Torr. By inorganic material, it is meant that the material contains at least one metal ion or atom. As used herein, all atoms, other than hydrogen, oxygen, fluorine, chlorine, bromine, helium, neon, argon, krypton, xenon, and radon are considered to be metal atoms. Preferred metal atoms are the alkali metals, the alkaline earth metals, the transition elements, the lanthanides, the actinides, boron, aluminum, gallium, indium, thallium, silicon, germanium, tin, lead, phosphorous, arsenic, antimony, bismuth, selenium, tellurium, polonium, and astatine. In addition, carbon, nitrogen, sulfur, and iodine are considered metals, particularly in cases where they are bonded to other atoms via non-covalent bonds (e.g., ionic bonds and pi-pi bonds). Particularly useful inorganic materials are those which contain a metal selected from the group consisting of V, W, Fe, Ti, Si, Al, P, Sb, As, Ba, B, Cd, Ca, Ce, Cs, Cr, Co, Cu, Ga, Ge, In, Pb, Mg, Hg, Mo, Ni, Nb, Re, Ta, Tl, Sn, Ir, Rh, Th, Ru, Os, Pd, Pt, Zn, Au, Ag, and combinations thereof. Illustrative inorganic materials contemplated for use in the present invention also include metal ions or metal atoms which contain at least one active ligand. These metal ions or metal atoms which contain at least one active ligand can be polymerized to form a bond to a neighboring metal atom or ion, thereby forming a macromolecular complex, or they can be treated so that they interact with a functionality contained in the polymer matrix to form, for example, a metal species stabilized via complexation by the polymer matrix""s functionality. Such metal ions or metal atoms include metallo-oxo species, metallo-nitro species, pi-allyl and arene complexes of Group IIIa, IVa, Va, VIa, VIIa, and VIIIa metals, and organo-metallo complexes ligated to organic functionalities like chlorides, bromides, alkyls, aryls, carboxylic acids, carbonyls, alkoxides, pyridines, tetrahydrofurans, and the like.
Preferably, the inorganic material is in the form of a macromolecular network or interacted with a functionality contained within the polymer matrix. The macromolecular networks and interacted inorganic materials are preferably stable to diffusion out of the polymer matrix at temperatures at which the composite is to be employed. For example, where the composite of the present invention is to be used as a catalyst, it is advantageous that the inorganic macromolecular network or inorganic material interacted with a functionality contained within the polymer matrix be stable to diffusion at temperatures employed in carrying out the particular catalytic reaction.
Suitable functionalities with which the inorganic material can interact include halogens (such as fluorines or chlorines), amines, alkenes, alkynes, carbonyls (such as keto groups, aldehyde groups, carboxylic acid groups, ester groups, amide groups, and the like), alcohols, and thiols. Inorganic molecules which are interacted with functionalities on the polymer matrix can have the formula Myxe2x80x94Xj, where X is a functionality contained within the polymer matrix (e.g., halogen, such as F or Cl, NH2, NH, Oxe2x80x94Cxe2x95x90O, Cxe2x80x94OH, Cxe2x95x90C, Cxe2x89xa1C, or Cxe2x95x90O), y is the oxidation state of the metal, which can range from zero to the highest oxidation state of the particular metal, and j is the number of ligands (e.g., 1-8) to which the particular metal can ligate within a given polymer matrix. For example, where M is Pd, and X is Cl, j can be 2.
Illustrative inorganic macromolecular networks which are stable to diffusion include metal atoms and macromolecular networks. Macromolecular networks, as used herein, are molecules containing three or more, preferably more than about 20, more preferably more than about 100, metal atoms that are directly or indirectly bonded together. Suitable macromolecular networks include polycondensates, such as those having the formula [X(O)nxe2x80x94Oyxe2x80x94X(O)n]m, wherein m is an integer from about 1 to about 10,000; X represents a metal ion having a charge of +s; s is an integer from 1 to the metal""s highest attainable oxidation state; y is an integer from 0 to s; and n is between zero and s/2. The well-known silica, titania, and zirconia structures, in which each metal atom is bonded to four oxygen atoms and each oxygen atom is bonded to two metal atoms, are examples of such macromolecular networks. Other macromolecular networks, such as those in which one or two of the bonds to some of the metal atoms in a silica, titania, or zirconia network are occupied by other moieties, such as alkyl or aryl groups, (e.g., macromolecular networks having the formula [xe2x80x94Si(R1)(R2)xe2x80x94Oxe2x80x94]m, where R1 and R2 are independently selected from alkyl and/or aryl groups and m is an integer from 2 to about 10,000) are also contemplated. Other macromolecular networks include those formed from pi-allyl compounds, such as pi-allyl compounds of Group IIIa, IVa, Va, VIa, VIa, and VIIIa metals. Illustrative pi-allyl compounds suitable for use in the practice of the present invention are described, for example, in Wilke et al., Angewandte Chemie, International Edition, 5(2):151-266 (1996), which is hereby incorporated by reference. In particular, these compounds are contemplated as being useful for forming conductive zero-valent macromolecular metal networks (e.g. macro molecular networks of conducting metals in the zero oxidation states), such as those having the formula (Moxe2x80x94Mo)n, wherein n is from about xc2xd to about 10,000 and Mo is a Group IIIa, IVa, Va, VIa, VIIa, or VIIIa metal.
Any suitable organic material can also be employed. Preferred organic materials suitable for use in the practice of the present invention are those capable of having a vapor pressure greater than zero at a temperature between room temperature and the thermal decomposition temperature of the polymeric matrix material. It is preferred that they also be capable of polymerizing into a macromolecular network (e.g., macromolecular networks having the formula (Rxe2x80x94R)n, wherein n is an integer from about 1 to about 10,000 and R is a monomer radical), such as through an oxidation, hydrolysis, chemical, electrochemical, or photochemical process. Organic molecules, such as pyrrole, aniline, and thiophene, that can be oxidatively polymerized, such as to form polypyrrole, polyaniline, and polythiophene, are suitable. Other suitable organic molecules are those which can be polymerized by exposure to actinic radiation (e.g., ultraviolet radiation), such as acetylene, which when polymerized forms polyacetylene. Still other illustrative organic molecules include organic monomers which can be converted to organic macromolecules, (i.e., polymers). These include the entire class of organic monomers which can be polymerized to form polymers, such as conducting polymers. A list of these materials, their properties, and their application to the construction of polymeric batteries, electric capacitors, electrochromic devices, transistors, solar cells, and non-linear optical devices and sensors can be found in: Yamamoto, xe2x80x9cMacromolecular Complexes: Dynamic Interactions and Electronic Processesxe2x80x9d, in E. Tsuchida, ed., Sequential Potential Fields in Electrically Conducting Polymers, New York:VCH Publishers, pp. 379-396 (1991) (xe2x80x9cYamamotoxe2x80x9d), which is hereby incorporated by reference.
Because of the close proximity of the polymer matrix and the inorganic or organic macromolecular network which exists within the natural free volume therein, the chemical functionality contained at the surface of the free volume within the polymer matrix can, in some instances, influence the chemical and electronic characteristics of the inorganic or organic macromolecular network and vice versa. Thus, by altering the polymer matrix, the properties of the inorganic or organic macromolecular network can be influenced. The degree of this influence depends on the nature of the chemistry and electronic properties of the starting polymer matrix. For example, strongly electron-withdrawing atoms, such as fluorine atoms, influence the catalytic properties of many metals. More particularly, Kowalak et al., Collect. Czech. Chem. Commun, 57:781-787 (1992), which is hereby incorporated by reference, reports that fluorinating zeolites containing polyvalent metal cations increases these zeolites"" activity for inducing acid catalyzed reactions. Therefore, where the composites of the present invention are to be used for their catalytic properties, it can be advantageous to employ matrix materials bearing strongly electron-withdrawing groups. In some cases, the polymer matrix can contain pendant groups or chemical functionalities located at the free volume interface which can influence the chemical or electronic properties of the inorganic or organic macromolecular network formed in the free volume. The interactions of the pendant groups or chemical functionalities with the macromolecular network contained in the natural free volume can be via through-space interactions (i.e., no actual bond or complex formation between the interacting species), via direct ionic, hydrogen, or covalent bonding, or, in some cases, via the formation of a bond which is commonly found when metal atoms coordinate with non-metals or other metallic atoms or groups. The formation of such bonds between the polymer matrix material and the macromolecular network contained within the polymer matrix material""s natural free volume can be detected using methods well known to those skilled in the art, such as ultraviolet-visible spectroscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, nuclear magnetic resonance spectroscopy, and other techniques, including those described in Drago, Physical Methods in Chemistry, Philadelphia:W. B. Saunders (1977), which is hereby incorporated as reference.
One of the advantages of composites of the present invention is that the properties of the starting polymer matrix are substantially preserved. In contrast to the results obtained by supercritical impregnation methods (which have the effect of swelling the polymer matrix material), preferred composites of the present invention (e.g., composites which contain inorganic or organic macromolecular networks disposed in the natural free volume of a polymer matrix) have dimensions which are substantially equal to the dimensions of the starting polymer matrix (i.e., the polymer matrix whose natural free volume contains no inorganic or organic macromolecular networks disposed therein). Preferred composites of the present invention also have flexibility, crystallinity, or thermal decomposition temperatures (xe2x80x9cTdxe2x80x9d) which are substantially the same as the flexibility, crystallinity, or Td of the starting polymer matrix. As used in this context, properties which differ by less than 10% are contemplated as being substantially the same. Td is described in Elias, Macromoleculesxe2x80x94Structure and Properties, I and II, New York:Plenum Press (1977), which is hereby incorporated by reference. In other situations, it may be desirable to modify these properties so that they are different than those of the starting matrix material. This can be done by choosing an appropriate inorganic or organic molecule. Alternatively or additionally, this can be achieved by subsequent chemical, photochemical, electrochemical, or thermal treatments which can act to initiate interactions between the chemical functionalities of the infused organic or inorganic macromolecular network and the chemical functionalities found at the free volume surface of the polymer matrix. These interactions can lead to, for example, enhanced catalytic activity of metal species in the macromolecular network, enhanced thermal properties of the composite compared with the initial thermal properties of the starting polymer matrix, or enhanced conductivity of an organic conducting macromolecular network. To enhance the conductivity of organic conducting macromolecular networks, the macromolecular network can be doped, for instance, by the chemistry contained in the polymeric matrix material (especially the chemical functionalities of the polymer matrix at the free volume interface) or, alternatively, by a subsequent diffusion of dopant, whereby a dopant molecule is incorporated into the composite. Suitable dopants that can be used to enhance the conductivity of conducting macromolecular networks disposed in the composites of the present invention can be found, for example, in Yamamoto, which is hereby incorporated by reference.
Although, as indicated above, preferred inorganic materials are those which are resistant to diffusion, the present invention is not intended to be limited thereto. For example, the inorganic material can be a compound which can be converted, such as by chemical (e.g. oxidation, hydrolysis or hydrogenation), or electrochemical, photochemical, or thermal methods, to an inorganic macromolecular network or to a metal species interacted with the polymer matrix""s functionality which resists diffusion. For example, the inorganic material can be a compound selected from the groups consisting of VOCl3, W(CO)6, Fe(CO)5, TiC4, SiCl4, AlCl3, PCl3, SbCl5, As(C2H5)3, Ba(C3H7)2, borane pyridine and tetrahydrofuran complexes, Cd(BF4)2, Ca(OOCCH(C2H5)C4H9)2, cerium (III), 2-ethylhexanoate, cesium 2-ethylhexoxide, chromium (III) naphthenate, CrO2Cl2, Co(CO)3NO, copper (II) dimethylaminoethoxide, triethylgallium, GeCl4, triethylindium, lead napthenate, C2H5MgCl, (CH3)2Hg, MoF6, Ni(CO)4, Nb(OC2H5)6, HReO4, Ta(OC2H5)5, C5H5Tl, SnCl4, pi-allyl compounds of Group IIIa, IVa, Va, VIa, VIIa, or VIIIa metals, and combinations thereof, all of which can be converted into inorganic materials which resist diffusion.
The polymer composites of the present invention can be prepared by the method which follows, to which the present invention also relates. A polymer matrix which has free volume therein is provided. The free volume is evacuated, and the evacuated free volume is infused with inorganic or organic molecules.
The free volume which is evacuated and into which the inorganic or organic molecules are infused can be natural free volumes (i.e., free volumes which are neither created nor modified by exposure of the polymer matrix to supercritical fluids under supercritical conditions prior to or during the evacuation or infusion).
Preferred inorganic molecules are those which can be converted into inorganic materials which are resistant to diffusion, such as inorganic molecules which can be polymerized into macromolecular networks or which can be treated so that the inorganic molecules interact with the polymer matrix""s functionality. Suitable inorganic molecules include compounds and complexes of metal atoms (such as the alkali metals, the alkaline earths, the transition elements, the lanthanides, the actinides, boron, aluminum, gallium, indium, thallium, silicon, germanium, tin, lead, phosphorous, arsenic, antimony, bismuth, selenium, tellurium, polonium, and astatine, and, particularly in cases where they are bonded to other atoms via non-covalent bonds (e.g., ionic bonds and pi-pi bonds), carbon, nitrogen, sulfur, and iodine), especially V, W, Fe, Ti, Si, Al, P, Sb, As, Ba, B, Cd, Ca, Ce, Cs, Cr, Co, Cu, Ga, Ge, In, Pb, Mg, Hg, Mo, Ni, Nb, Re, Ta, Tl, Sn, Ir, Rh, Th, Ru, Os, Pd, Pt, Zn, Au, Ag, combinations thereof, and their ions. The ligands to which the metal atom or ion is bonded or complexed is not particularly critical, though it is preferred that the ligand be chosen so that the inorganic molecule be labile through exposure to oxidizing, hydrolyzing, hydrogenating, chemical, or electrochemical environments, as well as being labile through exposure to heat or actinic radiation, such as ultraviolet radiation. Suitable ligands include those disclosed above. Specific examples of inorganic molecules which can be used in the practice of the present invention include VOCl3, W(CO)6, Fe(CO)5, TiCl4, SiCl4, AlCl3, PCl3, SbCl5, As(C2H5)3, Ba(C3H7)2, borane pyridine and tetrahydrofuran complexes, Cd(BF4)2, Ca(OOCCH(C2H5)C4H9)2, cerium (III), 2-ethylhexanoate, cesium 2-ethylhexoxide, chromium (III) naphthenate, CrO2Cl2, Co(CO)3NO, copper (II) dimethylaminoethoxide, triethylgallium, GeCl4, triethylindium, lead napthenate, C2H5MgCl, (CH3)2Hg, MoF6, Ni(CO)4, Nb(OC2H5)6, HReO4, Ta(OC2H5)5, C5H5Tl, SnCl4, pi-allyl compounds of Group IIIa, IVa, Va, VIa, VIIa, or VIIIa metals, and combinations thereof.
Suitable organic molecules are those which can be converted into polymeric materials which are resistant to diffusion, such as macromolecular networks. Suitable organic molecules include compounds such as, acetylene, p-phenylene, thiophene, 2,5-thenylene, pyrrole, 2,5-pyrrolylene, 3-substituted 2,5-thenylene, 3-substituted pyrrole, aniline, p-phenyl-enevinylene, 2,5-pyridinediyl, hexadiyne, and diaceytylenes. All of these compounds can be diffused into the polymer matrix and then oxidatively, chemically, or photochemically converted to their corresponding polymer so that they form a non-diffusible macromolecular network within the free volume of the polymer matrix. Since macromolecular networks made from these organic molecules can be electrically or ionically conducting, infusion of these organic molecules can add varying degrees of electrical and/or ionic properties to the composite material without significantly changing the crystallinity, flexibility, or Td of the starting polymer matrix material. Aromatic organic molecules, such as napthalenes and pyridines can also be infused to add optical properties to these materials. However, these aromatic materials cannot be polymerized into macromolecular networks and, therefore, are not as stable with respect to diffusion out of the polymer matrix, except in cases where they can complex with the polymer matrix""s functionality.
Other organic molecules which can be infused into the polymer matrix in accordance with the method of the present invention include silanes, such as alkoxysilanes and chlorosilanes, examples of which include tetraethoxysilane, tetramethoxysilane, and tetrachlorsilane. These organic molecules can be assembled into macromolecular networks by exposing the infused organic molecules to condensation conditions. Using these organic molecules permits one to produce an organic polymer matrix having an inorganic silica network disposed in the polymer matrix""s free volume.
Still other organic molecules which can be infused into the polymer matrix in accordance with the method of the present invention include alkylalkoxysilanes and alkylchlorsilanes and other molecules having the formula Si(R1)(X)3 or having the formula Si(R1)(R2)(X)2 where R1 and R2 are independently selected from an alkyl group or aryl group and each X is independently selected from a halogen (e.g., chlorine) and an alkoxy group (e.g., methoxy, ethoxy, and phenoxy). Particular examples of such organic molecules include dimethyldichlorosilane, dimethyldimethoxysilane, diethyldichlorosilane, diethyldiethoxysilane, and methylethyldimethoxysilane. These organic molecules can be assembled into macromolecular networks by exposing the infused organic molecules to condensation conditions, well know to those skilled in the art. Using these organic molecules permits one to produce an organic polymer matrix having an inorganic quasi-silica network disposed in the polymer matrix""s free volume. In the case where the organic molecules have the formula Si(R1)(R2)(X)2, it has been noted that the resulting composite exhibits increased slipperiness vis a vis the counterpart non-infused polymer matrix. This is particularly evident in cases where the polymer matrix is a halopolymer (such as MFA) or a nylon polymer. Although not wishing to be bound by theory, it is believed that the increased slipperiness can be due to changes in surface energy, lubricity, non-stick properties, coefficients of static friction, and/or coefficients of dynamic friction.
As indicated above, the free volume of the polymer matrix is first evacuated. As used herein evacuating means reducing the pressure in the free volume of the polymer matrix to less than atmospheric pressure (i.e., less than 760 Torr). This can be carried out by placing the polymer matrix in a chamber, vessel, or other container capable of withstanding the vacuum being employed and reducing the pressure in the chamber, vessel, or other container to less than about 760 Torr, more preferably from about 100 Torr to about 10 mTorr or less, and most preferably from about 1 Torr to about 10 mTorr or less. Evacuation is typically achieved in from about 1 minute to about several days, depending on temperature and pressure.
The free volume, thus evacuated, is then infused with the inorganic or organic molecules. In contrast to the methods of the prior art, the infusion here is carried out under non-supercritical conditions (e.g., in the absence rather than in the presence of supercritical and carrier fluids, under conditions which do not produce created free volume and associated polymer swelling, and the like).
The infusion can be carried out by any practical method. Most conveniently, the infusion is carried out with the inorganic or organic molecule in a gaseous state by contacting the evacuated polymer matrix with the gaseous inorganic or organic molecule. The inorganic or organic molecule can be naturally in the gaseous state, as is the case with some of the metal carbonyls, or the inorganic or organic molecules can be boiled, sublimed, or otherwise vaporized, such as with heat or under reduced pressure or both. In many cases the inorganic or organic molecules will be at least somewhat reactive with the air; in these cases, vaporization, as well as all other manipulations of the inorganic or organic molecules, are best conducted in an inert atmosphere, such as under argon or nitrogen, or in a vacuum.
The gaseous inorganic or organic molecule is then contacted with the evacuated polymer matrix. This can be carried out by placing the polymer matrix into a vessel, evacuating the vessel to a pressure less than 760 Torr, and then flowing the gaseous inorganic or organic molecules into the evacuated vessel containing the evacuated polymer matrix. Infusion can be accelerated and, generally, more of the gaseous molecules can be infused by effecting the infusion process in a atmosphere of pure gaseous inorganic or organic molecules, preferably at elevated temperatures. The temperature and pressure at which the infusion is effected is important because they affect the time required for the infusion process. Temperature and pressure are preferably optimized within a range that allows the inorganic or organic materials to have vapor pressures of greater than zero and increases the concentration of amorphous regions within the polymer (which provides for more free volume).
It is believed that, by initially evacuating the vessel holding the polymer matrix, the rate of infusion of the inorganic or organic molecules is enhanced, because the inorganic or organic molecules do not need to displace ambient gases residing in the polymeric matrix""s free volume.
In a preferred embodiment of the present invention, infusion is carried out at temperatures greater than about 50xc2x0 C. below that of the polymer matrix""s glass transition temperature (xe2x80x9cTgxe2x80x9d) and less than the thermal decomposition temperature (xe2x80x9cTdxe2x80x9d) of the starting polymer matrix material (ie., at temperatures greater than about Tgxe2x88x9250xc2x0 C. but less than about Td). The greater the temperature, the greater the rate of incorporation of the inorganic or organic molecules infused into the polymer matrix. Also, the greater the temperature, the greater the resulting concentration of inorganic or organic material diffused into the polymer matrix due to thermal expansion which acts to increase the free volume within the polymer matrix. It is to be understood that these are only preferred conditions and that the same processes can be carried out outside of these preferred temperature ranges. In some cases, effecting infusion outside this temperature range may be preferred, such as to control the concentration of the inorganic or organic molecules in the finished composite. As the skilled practitioner will note, in order to practice the present invention in the preferred temperature range, the inorganic or organic molecule must have a non-zero vapor pressure at temperatures greater than about Tgxe2x88x9250xc2x0 C. but less than about Td of the polymer matrix and/or at the pressure used during the infusion process. In some cases, heating the polymer matrix to temperatures which optimize free volume space may result in thermal decomposition of the inorganic or organic molecules one wishes to infuse into the polymer matrix. In such cases, infusion is best carried out at temperatures and pressures at which the inorganic or organic molecules can achieve a vapor pressure of greater than zero but not thermally decompose. As indicated above, the time required for infusion varies depending on the temperature, the pressure, the nature of the inorganic or organic molecules, the nature of the polymer matrix, the desired degree of infusion, the desired concentration of inorganic or organic molecules, and the like. In most circumstances, infusion can be effected in from about a few minutes to about 2 days.
Optionally, the method of the present invention can include a step of infusing a second, different inorganic or organic molecule. This infusing step can be carried out simultaneously with the above-described infusing step. Alternatively, this infusing step can be carried out subsequent to the above-described infusing step. For example, the free volume is evacuated; a first inorganic or organic molecule is infused; and, thereafter, while maintaining the free volume in an evacuated state, a second, different inorganic or organic molecule is infused. Alternatively, the free volume is evacuated; a first inorganic or organic molecule is infused; the free volume is permitted to become non-evacuated, for example by exposure of the composite to ambient atmosphere, to effect, for example, polymerization of the infused inorganic or organic molecules and assembly thereof into macromolecular networks (as described in more detail below); the free volume is evacuated; and a second, different inorganic or organic molecule is infused.
Where simultaneous infusion of two different infusants, A and B, is to be carried out, this can be conveniently effected by placing A and B in the same flask (when A and B can both be volatilized at about the same temperature). Alternatively, (in cases where A and B have different volatilization temperatures), A can be placed in one flask, B can be placed in another flask, and each flask can be heated simultaneously but individually to the temperature at which its contents volatilize. , and the flask containing A can be heated to a temperature at which A volatilizes; and B in the another flask (when A and B can both be volatilized at about the same temperature).
Where sequential infusion of two different infusants, A and B, is to be carried out, this can be conveniently effected by placing A and B in the same flask (when A and B volatilize at significantly different temperatures). The flask is then heated to about the volatilization temperature of the material with the lower volatilization temperature, and the flask is maintained at about this temperature for a period of time. Then, the temperature of the flask is raised to the the volatilization temperature of the material with the higher volatilization temperature, and the flask is maintained at about this temperature for a period of time. Alternatively, sequential infusion of two different infusants, A and B, can be carried out by placing A and B in separate flasks. Each flask can then be heated sequentially to the repective volatilization temperature of its contents.
After infusing the inorganic or organic molecules into the polymer matrix, the inorganic or organic molecules can be polymerized under conditions effective to cause the inorganic or organic molecules to assemble into macromolecular networks. Preferably, the polymerization is carried out in the absence of free (i.e., non-infused) inorganic or organic molecules. Consequently, it is preferred that, prior to polymerization, the infused polymer matrix be removed from the atmosphere containing gaseous inorganic or organic molecules or that the atmosphere surrounding the infused polymer matrix be evacuated or replaced with an inert gas.
Polymerization can be carried out by exposing the inorganic or organic molecules infused in the free volume of the polymer matrix to any suitable polymerizing condition. For example, the infused inorganic or organic material can be oxidized, hydrolyzed, hydrogenated, chemically treated, photoactivated, electrochemically polymerized, or thermally polymerized by exposing the infused inorganic or organic material to appropriate conditions, such as by exposing the infused inorganic or organic material to an oxidizing agent, a hydrolyzing agent, a hydrogenating agent, a specific chemical, actinic radiation, suitable voltages, or appropriate temperatures.
Typically, the oxidizing, hydrolyzing, or hydrogenating agent is gaseous or is contained in vapor form in an inert gas. For convenience, oxidation or hydrolysis can be effected by exposing the inorganic molecules to a gas which includes water, oxygen or combinations thereof, such as ambient air. The oxidation, hydrolysis, or hydrogenation can be carried out at any convenient temperature or pressure, preferably at room temperature and ambient pressure and at temperatures below the polymer matrix""s Td and the inorganic or organic molecules decomposition temperature. In the case where the inorganic or organic molecules are air or moisture sensitive, oxidation or hydrolysis can be conveniently carried out at ambient pressure and temperature and in ambient air in from about 5 min to about 48 hours.
Hydrogenation can be carried out by exposing the infused polymer matrix to hydrogen gas. For example, a polymer matrix containing a metal pi-allyl compound can be placed in an atmosphere of hydrogen gas at room temperature for from about 5 minutes to about 48 hours. The pi-allyl compound is reduced, propane gas is released, and a stabilized metal species or a metal network is formed in the free volume of the polymer matrix. In the case where a metal network is formed in the polymer matrix""s free volume, the metal network may or may not interact with functionalities contained within the polymer matrix.
In some cases polymerization can be carried our chemically. For example, organic molecules of pyrrole can be infused into the polymer matrix""s free volume and then converted to polypyrrole by contacting the matrix material with a chemical solution containing 50% water and 50% HNO3. This solution oxidizes the pyrrole to a macromolecular network of polypyrrole which resides throughout the free volume of the polymer matrix. Alternatively, the polymer matrix can be first converted to a composite as described herein such that the macromolecular network contained in the polymer matrix has oxidative properties. One suitable macromolecular network having oxidative properties is V2O5. After formation of this composite containing V2O5, organic molecules like pyrrole can be infused, which then are oxidized by the V2O5 macromolecular network to form a macromolecular polypyrrole network within the polymer matrix""s free volume.
Organic monomers which can be electrochemically polymerized, such as acetylene or thiophene, once infused into the free volume of the polymer matrix, can be polymerized by contacting the infused polymer matrix with an electrode and adjusting the potential of the electrode to facilitate oxidative polymerization of the organic molecules.
As a further example, thermal treatment of the organic molecule C6H4xe2x80x94CH2xe2x80x94(R2xe2x80x94S+Xxe2x88x92)xe2x80x94CH2xe2x80x94 facilitates polymerization to the macromolecular polymer polyphenylenevinylene. (See, for example, Yamamoto, which is hereby incorporated by reference.)
Another method for polymerizing infused organic molecules into macromolecular networks involves using a composite of the present invention in which a catalyst is disposed in the polymer matrix""s free volume. Such a composite can be produced using the above-described methods of the present invention by, for example, infusing a catalyst, such as a photocatalyst, into the polymer matrix""s free volume prior to, during, and/or subsequent to infusing the organic molecules into the polymer matrix""s free volume. Suitable photocatalysts include, for example, titanium compounds and/or vanadium compounds, such as TiCl4, TiO2, Ti(OR)4, where each R is, independently, an alkyl group or an aryl group, VOCl3, VO2, VO(OR)3, where each R is, independently, an alkyl group or an aryl group, or combinations thereof. Preferably, the catalyst (e.g., the photocatalyst) is in a form which prevents it from diffusing out of the polymer matrix""s free volumes. For example, it is preferred that the catalyst be in the form of a macromolecular network or in a formn that is interacted with the polymer matrix""s functionality. Illustratively, a polymer matrix having a catalyst in the form of a macromolecular network disposed in the polymer matrix""s free volume can be made by providing a polymer matrix having free volume therein, wherein the polymer matrix is at least partially amorphous; evacuating the free volume of the polymer matrix; infusing a catalyst precursor into the evacuated free volume; and polymerizing the catalyst precursor under conditions effective to assemble the catalyst precursor into a catalyst in the form of a macromolecular network. Selection of the catalyst precursor will depend, of course on the nature of the catalyst desired. Typically, the catalyst precursor will be one that is or can be converted into the gaseous phase (typically by heating) and that can be assembled into macromolecular networks, for example, by hydrolsis, etc., as described above. For example, where the catalyst is a V2O5 macromolecular network, suitable catalyst precursors are VOCl3, VO2, VO(OR)3, and assembly into macromolecular networks can be achieved by hydrolysis, such as by exposure to ambient air.
Once the catalyst and organic molecules are infused into the polymer matrix""s free volume, the composite is exposed to conditions effective to activate the catalyst and polymerize the organic molecules into a macromolecular network. Optimal conditions to activate the catalyst and effect polymerization will, of course, depend on the nature of the catalyst and the nature of the material being polymerized into macromolecular networks. For example, where the catalyst is a photocatalyst, activation is optimally achieved by exposure to light, for example, in the case of a V2O5 photocatalyst, by exposure to ultraviolet light. By using this method and a fluoropolymer precursor (e.g., vinylidene difluoride), composites containing fluoropolymer macromolecular networks can be produced. Such composites are believed to have increased chemical resistance, increased inertness, and increased hydrophobicity. Such composites also have reduced permeability, as the free volumes which permit, for example, gases to diffuse through the polymer are filled or partially filled with the macromolecular network. Composites having reduced permeability are particularly useful in anti-corrosion applications, where, for example, oxygen migration through permeable polymers is a critical component in the corrosion process of the substrate to which the polymer is adhered, thus weakening the adhesive bond and/or deteriorating the substrate. In particular, it is contemplated to use this method to produce a halopolymer macromolecular network in the free volumes of a halopolymer matrix, thus reducing or preventing gas (particularly oxygen) migration through the halopolymer matrix.
Once polymerized, the inorganic or organic molecules self-assemble into macromolecular networks over a period of time ranging from simultaneous assembly upon exposure to the polymerizing conditions to a few hours to a few days.
The assembled macromolecular network can, optionally, be infused with dopants, such as Na, I2, Br2, FeCl3, AlCl3, AsF5, and those disclosed in Yamamoto, which is hereby incorporated by reference, to enhance the conductive properties of the macromolecular network contained within the free volume of the polymer matrix. Further description of these processes and their utility in making, for example, polymeric batteries, electrolytic capacitors, electrochromic devices, diodes, solar cells, and non-linear optic materials, can be found in Yamamoto, which is hereby incorporated by reference.
It is believed that, because the inorganic or organic molecules which are diffused into the polymer matrix are confined to the polymer matrix""s free volume, the resulting self-assembled macromolecular networks are mainly limited to extending lengthwise (i.e., only a monolayer to a few layers of the network can form in two dimensions and the growth of the network is mainly through a one dimensional extension of a single monolayer chain through the interconnected free volumes contained within the polymer matrix). It is further believed that this results in a material whose polymer matrix phase is relatively unchanged with respect to flexibility, crystallinity, Td, and other physical properties. In essence, the polymer matrix is believed to act only as a molecular template into which the inorganic network is formed along the free volume space associated with these materials. However, since the inorganic or organic macromolecular network is contained in free volumes which are homogeneously incorporated throughout the polymer matrix, it imparts its own properties to the composite as a whole. Such imparted properties include controlled and varying optical densities, catalytic properties, and electrical and ionic conductivities, as well as enhanced thermal-mechanical properties.
Alternatively, particularly in cases where the polymer matrix contains a suitable functionality, the infused inorganic or organic molecules can be treated under conditions effective to cause the inorganic or organic molecules to interact with the polymer matrix""s functionality. As described above, suitable polymer matrix functionalities include halogens (such as fluorines or chlorines), amines, alkenes, alkynes, carbonyls (such as keto groups, aldehyde groups, carboxylic acid groups, ester groups, amide groups, and the like), alcohols, and thiols. Inorganic molecules which are interacted with functionalities on the polymer matrix can have the formula MyXj, where X is a functionality contained within the polymer matrix (e.g., halogen, such as F or Cl, NH2, NH, Oxe2x80x94Cxe2x95x90O, Cxe2x80x94OH, Cxe2x95x90C, Cxe2x95x90C, or Cxe2x95x90O), y is the oxidation state of the metal, which can range from zero to the highest oxidation state of the particular metal, andj is the number of ligands (e.g., 1-8) to which the particular metal can ligate within a given polymer matrix. For example, where M is Pd, and X is Cl, j can be 2. In cases where the inorganic or organic molecules contain metal atoms or ions, the interacted metal and polymer matrix functionality can generally be characterized as an inorganic complex, although other types of interactions, such as covalent interactions, ionic interactions, pi-pi electronic interactions, and the like are also contemplated.
As indicated above, the polymer matrix""s functionality can be a carboxylic acid functionality, which, as used herein, is meant to include carboxylic acid groups, carboxylic acid ester groups, and carboxylic acid amide groups. Suitable polymer matrices include a polyacetate, a polycarbonate, as well as the polymer matrices mentioned hereinabove. Combinations of these polymers (e.g., copolymers) are also suitable. The inorganic or organic molecules which can be infused into the polymer matrix""s free volume can be bifunctional, i.e., they can contain two or more functional groups. The two or more functional groups in the inorganic or organic molecules can all be the same (e.g., each is an amine group); they can all be different (e.g., one amine group, one carboxylic acid group, and one silyl group), or two or more can be the same and different from a third functional group (e.g., two are amine groups and one is an acid group). Suitable organic bifunctional molecules include molecules which include more than one amine group, more than one acid group, or at least one amine group and at least one acid group. One class of suitable bifunctional molecules is the alkylene diamines, which are meant to include alkanes (e.g., ethane, linear, branched or cyclic propane, butane, pentane, hexane, octane, nonane, decane, dodecane, etc), bearing two amine groups. As used in this context, amine is meant to include unsubstituted amines (e.g., having the formula xe2x80x94NH2), monosubstituted amines (e.g., having the formula xe2x80x94NHR where R is, for example, an alkyl or aryl group), and disubstituted amines (e.g., having the formula xe2x80x94NRRxe2x80x2 where R and Rxe2x80x2 are independently selected from, for example, alkyl or aryl groups). Illustrative examples of suitable bifunctional organic molecules include those having the formula R1xe2x80x94NHxe2x80x94R2xe2x80x94NR3R4 where R1, R3, and R4 are independently selected from the group consisting of H, alkyl, and aryl and R2 is a C2-C10 alkylene moiety, preferably a xe2x80x94CH2CH2xe2x80x94 moiety, such as is the case where the bifunctional organic molecule is ethylene diamine.
The method of the present invention can also be used to introduce fluorinated functionality into a polymer matrix that does not otherwise have fluorinated functionality. For example inorganic or organic molecules used in the method described above can contain an amine or acid functionality and a fluorinated alkyl or aryl moiety. Examples of such compounds include fluorinated alkylamine (e.g., a perfluorinated alkylamine such as pentafluoropropylamine) or a fluorinated carboxylic acid (e.g., a trifluoroacetic acid). By using carboxylic acids or amines containing fluorinated alkyl groups, water and/or stain repellence can be imparted to the polymer matrix (e.g., a polyester matrix). Furthermore, since the method of the present invention provides for covalent interaction between the polymer matrix""s functionality and the organic molecules, the resulting composite is more stable in terms of, for example, its repellency compared to surfactant-based repellants, which are typically held via electrostatic or ionic bonds. Treatment with trifluoroacetic acid would create a dyeable material which is also water and stain repellant in one step.
The method of the present invention can also be practiced with an aminoalkylalkoxysilane organic molecule, such as an aminoalkyltrialkoxysilane organic molecule (e.g., aminopropyltriethoxysilane or aminohexyltrimethoxysilane). Treatment of the polymer matrix, as described above, with silane coupling agents, such as aminoalkyltrialkoxysilanes, produces polymer matrices bearing covalently attached pendant groups terminated with a trialkoxysilyl (e.g., trimethoxysilyl and/or triethoxysilyl) functionality. The trialkoxysilyl functionality can be used to improve adhesion of the polymer matrix (e.g., polyester) to other materials including glass, fabrics, and polymer resins, such as phenolic resins. Specific examples of suitable aminoalkyltrialkoxysilanes for use in the practice of this aspect of the present invention include, for example, aminopropyltrimethoxysilanes, aminopropyltriethoxysilanes, and aminoethylaminopropyltrimethoxysilanes. Optionally, contacting can be carried out such that the silane coupling agent reactant enters the free volumes of the polymer matrix and the amine functionality of the silane coupling reactant reacts with the polymer matrix""s functionality (e.g., an ester group) in the free volumes thereof. Alternatively or additionally, it can be advantageous to permit or induce the trialkoxysilyl functionality of the silane coupling agent to interact so as to form a xe2x80x94Sixe2x80x94Oxe2x80x94Sixe2x80x94 macromolecular network through at least a portion of the polyester""s free volume. In this manner, the silane coupling reactant can be made to become particularly well attached to the polymer matrix. Treatment of the polymer matrix (e.g., polyester) with an organic diamine or triamine, as described above, can also be used to promote adhesion of the polymer to materials which are reactive with amine functionalities, such as, for example, materials containing aldehyde or epoxide functionality.
In the case where bifunctional organic molecules are used, the method of the present invention is also particularly well adapted to further bonding other materials to the uninteracted functionality of the bifunctional organic molecule. In this case, it is preferred that the inorganic or organic molecules include a first functional group which is capable of interacting with the polymer matrix""s functionality (e.g., an amine, in the case where the polymer matrix contains carboxyl functionality, such as a polyester polymer matrix) and a second functional group. The second functional group can be one capable of interacting with the polymer matrix""s functionality (e.g., an amine group, in the case where the polymer matrix contains carboxyl functionality, such as a polyester polymer matrix), or it can be one that is not capable of interacting with the polymer matrix""s functionality (e.g., an acid group, in the case where the polymer matrix contains carboxyl functionality, such as a polyester polymer matrix). In the latter case, of course, the second functional group does not interact with the polymer matrix""s functionality, whereas, in the former case, the treating step is carried out in such a manner such that the second functional group does not interact with the polymer matrix""s functionality. This can be achieved, for example by using a large excess of bifunctional inorganic or organic molecules (relative to the number of functionalities on the polymer matrix), or by using protecting groups (which, preferably, are readily cleavable), etc. As a result, in the above-described preferred embodiment, only one of the bifunctional molecule""s functional groups is interacted with the polymer matrix""s functionality, while the other functional group is available for further chemistry, for example, with a functionalized compound. Choice of the functionalized compound will depend on the nature of the inorganic or organic molecules"" second functional group. Illustratively, in the case where the inorganic or organic molecules"" second functional group is an acid group, the functionalized compound can be any compound capable of reacting with acid groups (e.g., hydroxy-containing compounds, amine-containing compounds, metal containing compounds, etc. The nature of the bond formed between the inorganic or organic molecules"" second functional group and the functionalized compound is not critical to the practice of this aspect of the present invention, and such bonding can be, for example, covalent bonding, ionic bonding, sigma-pi bonding, pi-pi bonding, etc.
For example, the polymer matrix having a bifunctional molecule bonded thereto can be reacted with a acidic or basic dyestuff under conditions effective for the dyestuff to ionically bond to the bifunctional organic molecule""s uninteracted amine or acid functionality. The acidic or basic nature of the pendant groups can be used to dye the polyester material employing any known acidic or basic dye stuffs. That is, acidic dyes can react with the basic sites generated from aminolysis and basic dyes can react with acidic sites generated from acidolysis. The dyeing process typically creates an ionic bond between the dye molecule and the covalently attached pendant group. By judicious choice of reactants, additional acidic or basic binding sites can be created. For example, reaction with ethylenediamine leads to a single pendant group containing both a primary and secondary basic amine site. Likewise, reaction with maleic acid results in a pendant carboxylic acid group at each newly formed pendant group. These reactions should facilitate the uptake of dyes and make the dyeing of polyester materials more facile.
In yet another aspect of the present invention, the polymer matrix having a bifunctional molecule bonded thereto can be reacted with a metal-containing antimicrobial agent under conditions effective for the metal-containing antimicrobial agent to chelate with the compound""s uninteracted amine or acid functionality. As indicated above, treatment of the polymer matrix with organic diamines, such as alkylene diamines (e.g., ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, etc.), creates a polymer matrix having pendant bidentate ligands capable of chelating selected metal ions. Alternatively, treatment with organic triamines (e.g., diethylenetriamine) creates a pendant tridentate chelating ligand. The strength of the chelate formed would determine the rate at which selected metal ions would be released from the polymer matrix. This rate could be controlled by varying the groups attached to the nitrogen atoms. Therefore, binding with of known antimicrobial agents, such as Ag+, Zn2+, and Sn4+, or other metal or metal containing materials (e.g., those set forth in U.S. Pat. No. 6,015,816 to Kostyniak, et al., which is hereby incorporated by reference) can be used to produce a polymer matrix possessing anti-microbial properties. Such binding can be effected, for example, by contacting an appropriate metal salt, preferably in solution, with the pendant chelating ligand. The anti-microbial properties would be expected to be more permanent than other ionic or electrostatic treatments because the metal ions would be more tightly bound to the covalently attached pendant groups. The release of these metal ions would be gradual, with the rate of release governed by the formation constant (Kf) of the metal chelate complex. In addition to modifying the rate of release of the metal by varying the nature of the chelating ligand (e.g., tridentate vs. bidentate) or by varying the groups attached to the nitrogen atoms, the rate of release can be additionally or alternatively modified, for example, by changing the oxidation state of some or all of the metal ions (e.g., by exposing the complexed ions to a mild reducing agent). Antimicrobial polymer matrices can also be prepared by using organic diacid or triacid reactants, followed by subsequent binding of suitable known anti-microbial agents.
As indicated above, the method of the present invention can be used to produce composites in which the infused inorganic or organic molecules have a residual functionality anchored in the free volume of the polymer matrix by virtue of an interaction of the inorganic or organic molecule with the polymer matrix""s functionality (e.g., by using bifunctional inorganic or organic molecules) or by virtue of the formation of a maromolecular network (e.g., by using an aminoalkylalkoxysilane organic molecule). Such composites in which the infused inorganic or organic molecules have a residual functionality anchored in the free volume of the polymer matrix can be used to improve bonding of the polymer matrix to surfaces, particularly to surfaces having a surface functionality that is capable of forming bonds (e.g., covalent bonds, ionic bonds, van der Waals bonds, hydrogen bonds, chelation bonds, pi-pi bonds, sigma-pi bonds, etc.) with the composite""s pendant functionality. Such surfaces can have such surface functionality as an intrinsic property of the material from which they are made, or they can be modified so as to introduce such surface functionality. For example, in the case where the composite""s pendant functionality is an amine group, the surface functionality can be a functional group which interacts with amine groups, such as an epoxy group. Where the surface is one that does not have such epoxy functionality, such epoxy functionality can be provided by first coating the surface or a portion thereof (e.g., by spraying, brushing, dip-coating, etc.) with a material (e.g., an expoxy-containing alkoxysilane, such as glycidoxyalkyltrialkoxysilanes, for example, glycidoxypropyltrimethoxysilane (xe2x80x9cGOPSxe2x80x9d) ) that bonds to the suface and that provides the desired epoxy functionality. Other suitable combinations of surface functionality and pendant functionality include: amine/isocyanate, alcohol/isocyanaye, amine/aldehyde, and amine/benzylhalide. Surfaces that can be coated using this method include metal (e.g., carbon steel, iron, galvanized steel, aluminum, tantalum, titanium, etc.) surfaces, fiberglass surfaces, plastic surfaces, and the like. Application of the composite to the surface can be effected by any conventional method. Where the composite is in the form of sheet goods (e.g., in the form of a film), it can be applied by simply rolling the composite onto the surface. Where the composite is in the form of a powder or beads, application of the composite to the surface can be effected by conventional coating methods, such as spraying (e.g., plasma spraying, flame spraying, etc.), dip-coating, electrostatic coating, dispersion coating, brushing, rolling, and the like.
The interaction between the inorganic or organic material and the polymer matrix""s functionality can be spontaneous, i.e., it can occur immediately or over a period of time simply by virtue of the inorganic or organic material being in close proximity with the polymer matrix""s functionality. In this case, treating simply means permitting the inorganic or organic molecules to interact with the polymer matrix""s functionality. In other cases, the interaction between the inorganic or organic material is not spontaneous and requires that the inorganic or organic molecules be actively treated, such as by oxidizing, hydrolyzing, hydrogenating, chemically treating, or photoactivating, electrochemically activating, the infused inorganic or organic molecules. The oxidized, hydrolyzed, hydrogenated, chemically treated, photoactivated, electrochemically activated inorganic or organic molecules then go on to interact with the functionality of the polymer matrix. In practicing this aspect of the present invention, oxidizing, hydrolyzing, hydrogenating, chemically treating, or photoactivating, electrochemically activating the infused inorganic or organic molecules can be carried out by the methods described above in regard to polymerizing the inorganic or organic molecules.
In some cases, most notably in the cases where the inorganic molecules contain metal atoms and ligands bonded thereto where the metal ligand bond strength is large, oxidation, hydrolysis, or hydrogenation of the ligands may be slow or incomplete. For comparisons of metal ligand bond strength and the tendency for metals to hydrolyze see Huheey, Inorganic Chemistry, 3rd Edition, Principles of structure and reactivity, New York:Harper and Row, Chapters 7 and 11, which is hereby incorporated by reference. In these cases, it is advantageous to expose the inorganic molecules to actinic radiation, such as ultraviolet (xe2x80x9cUVxe2x80x9d) radiation, preferably a broad band source of about 190 nm to about 400 nm, (or, in some cases, high energy UV (e.g., wavelengths less than 190 nm) or x-radiation), under conditions effective to cleave the ligands from the metal atoms, typically for a period of time related to the strength of the metal ligand bond and the power output (i.e., power density) of the radiation source.
The metal atoms having the ligands cleaved therefrom can be treated photochemically, chemically, electrochemically, or thermally under conditions effective to cause the metal atoms to interact with the polymer matrix""s functionality.
Alternatively, the metal atoms having the ligands cleaved therefrom can then be exposed to an oxygen or water containing gas under conditions effective to cause the metal atoms to assemble into macromolecular networks. An oxygen or water containing gas or atmosphere is preferably present while exposing the inorganic molecules (diffused into the polymer matrix) to actinic radiation, so that oxidation or hydrolysis can occur immediately upon cleavage of the ligand from the metal. Oxygen or water containing gases suitable for use in this process include: substantially pure oxygen; oxygen mixed with water and/or an inert gas, like Ar or N2; or ambient air.
For example, W(CO)6 is a tungsten metal complex which contains 6 carbonyl ligands. The carbonyl ligands are labile to heat or UV radiation. However, their lability decreases with the loss of each carbonyl ligand. In other words, upon loss of the first carbonyl, the second carbonyl becomes more difficult to remove; upon loss of the second carbonyl, the third carbonyl becomes more difficult to remove; and so on. Thus, after infusion of W(CO)6 into a polymer matrix, loss of the carbonyl ligands is preferably carried out by activating the tungsten-carbonyl bond by exposure to a broad band ultraviolet source (e.g., radiation between 190 nm and 400 nm) to facilitate the total decomposition of the W(CO)6. The decomposed tungsten complex is then free to interact with the polymer matrix""s functionality or to react with neighboring decomposed tungsten complexes to form a macromolecular tungsten oxide network.
It is believed that the forgoing polymerization of the inorganic or organic molecules and assembly into macromolecular networks and/or the foregoing treatment of the inorganic or organic molecules to cause their interaction with the polymer matrix""s functionality results in improved stability of the complex, such as, for example, by reducing migration of the inorganic or organic molecules out of the free volume of the polymer matrix.
The composites of the present invention are useful, for example, in the construction of lightweight, flexible, electromagnetic, UV and x-radiation shields; flexible components for use in the construction of electrochromic or liquid crystal based flat panel displays; and electrode and separator materials used in the construction of lightweight, high energy density batteries.
The composites of the present invention and composites produced in accordance with the method of the present invention, particularly those containing vanadium and oxygen, such as vanadium pentoxide, can be used as an electrically-conductive imaging layer of an electroconductive imaging element, such as those which are employed in high speed laser printing processes. The electroconductive imaging element typically includes an insulating support, an electrically-conductive layer overlaying the support, and a dielectric imaging layer overlaying the electrically-conductive layer. Further details regarding the construction and use of these electroconductive imaging elements can be found, for example, in Anderson I, which is hereby incorporated by reference.
The composites of the present invention and the composites made by the processes of the present invention, particularly those containing a vanadium oxide macromolecular network, can be used as antistatic materials in photographic elements, such as photographic films and papers. These photographic elements include a substrate, one or more light sensitive layers, and one or more anti-static layers containing the composite of the present invention. Other component layers, such as subbing layers, barrier layers, filter layers and the like can also be employed. A detailed description of photographic elements and their various layers and addenda can be found in, for example, James, The Theory of the Photographic Process, 4th ed. (1977), which is hereby incorporated by reference.
The present invention is also directed to a fuel cell, such as a battery. The fuel cell includes a composite of the present invention or a composite produced in accordance with the method of the present invention, particularly those that are electrically or ionically conductive. The fuel cell further includes an anode and a cathode which are in contact with the composite.
The present invention is also directed to a method for shielding a material from electromagnetic radiation emitted from an electromagnetic radiation source. The method includes disposing a composite of the present invention or a composite produced in accordance with the method of the present invention between the material to be shielded and the electromagnetic radiation source. Composites whose inorganic or organic molecule include a metal and liquid environment, such as those found in iron, titanium, and vanadium complexes, are particularly well suited for shielding visible and ultraviolet radiation. Composites whose inorganic or organic molecules include a metal having a high Z number, such as tungsten lead, and gold, also shield high-energy ultraviolet light and x-rays. As used herein, shielding is meant to include filtering, such as when the intensity of the electromagnetic radiation is partially reduced (e.g., by 50% or more), as well as blocking, such as when the electromagnetic radiation is completely absorbed by the composite.
Composites whose inorganic or organic molecules include both vanadium and titanium are particularly efficient at shielding UV radiation. In such composites the vanadium:titanium mole ratio can be between about 99.9:0.1 and 95:5, between about 95:5 and 90:10, between about 90:10 and 80:20, between about, 80:20 and 70:30, between about 70:30 and 60:40, between about 60:40 and 50:50, between about 50:50 and 40:60, between about 40:60 and 30:70, between about 30:70 and 20:80, between about 20:80 and 10:90, between about 10:90 and 5:95, and/or between 5:95 and 0.1 and 99.9. Suitable inorganic or organic molecules than contain vanadium include vanadium metal, vanadium ions, and vanadium compounds and complexes. Suitable inorganic or organic molecules than contain titanium include titanium metal, titanium ions, and titanium compounds and complexes.
The titanium and vanadium metal, ions, compounds, or complexes can be infused simultaneously or sequentially. In a particularly preferred method titanium and vanadium metal, ions, compounds, or complexes are infused simultaneously by selecting the titanium metal, ion, compound, or complex so that it volatilizes at about the same temperature as the vanadium metal, ion, compound, or complex. In this manner both infusants can be placed in a single vessel and simultaneously volatilized and infused by heating them to the temperature at which both materials volatilize.
The absorption spectrum of a particular composite containing inorganic or organic molecules capable of blocking UV radiation can be modified (and, thus, optimized for a particular application) by using complexes rather than free metal or ions (e.g., rather than titanium metal or ions or vanadium metal or ions). Suitable complexes include, for example, complexes of vanadium, complexes of titanium, or combinations thereof. Illustrative complexes include titanium and vanadium amines, titanium and vanadium phosphines, titanium and vanadium cyanides, titanium and vanadium cyanates, and titanium and vanadium isocyanates. Pluridentate ligands, such as diethylenetriamine, can also be employed to modify the absorption characteristics of the composite. Also useful are aminoalkyltrialkoxysilanes, such as aminopropyltrimethoxysilanes, aminopropyltriethoxysilanes, and aminoethylaminopropyltrimethoxysilanes. Where aminoalkyltrialkoxysilanes are employed, it can be advantageous to permit or induce the alkoxysilane groups to assemble into macromolecular networks in the free volumes of the polymer matrix or to interact with an appropriate functionality of the polymer matrix. Complexes of, for example, titanium and/or vanadium can be made by a variety of methods. In one method, the ligand (e.g., amine, phosphine, etc) is first infused into the free volumes using, for example, the method of the present invention; then, the metal (e.g., titanium or vanadium atom, ion, or compound) is infused; and the metal and ligand and permitted or induced to form a complex. Alternatively, the metal (e.g., titanium or vanadium atom, ion, or compound) can be infused first, followed by infusion of the ligand (e.g., amine, phosphine, etc). Still alternatively, the metal and ligand can be infused simultaneously. Still alternatively, in cases where the metal complex has a sufficiently high vapor pressure, the complex can be preformed and then infused, as the complex, into the polymer matrix""s free volume.
The composites of the present invention can also be used as a flame or heat retardant material. More particularly, composites which contain a zinc oxide, a zinc/molybdenum oxide, a zinc/chromium oxide, a zinc/silicon oxide, a zinc/titanium oxide, a bismuth/boron oxide, a molybdenum/tin oxide, a molybdenum oxide, an antimony oxide, alumina, or silica macromolecular network or combinations thereof can be used in place of the fluoropolymer composition described in U.S. Pat. No. 4,957,961 to Chandrasekaren et al., which is hereby incorporated by reference, to thermally insulate wires and jacketing cables and to protect them from flames and smoke. Accordingly, the present invention is also directed to a method for shielding a material from heat or flame. The method includes disposing a composite of the present invention or a composite produced in accordance with the method of the present invention between the material to be shielded and the source of heat or flame. As used herein, the heat or flame source can be an actual heat or flame source or a potential heat or flame source.
As indicated above, the composites of the present invention, especially those containing a macromolecular network in the polymer matrix""s free volume (e.g., a halopolymer macromolecular network in the free volume of a halopolymer matrix), are particularly useful as a coating material for a substrate to reduce or prevent corrosion of the substrate by, for example, preventing the permeation of moisture, oxygen, or other corrosive chemistry through the polymer matrix""s free volumes to the substrate. In another embodiment directed to reducing the adverse effects (e.g., corrosive effects) of oxygen on a substrate, the present invention relates to a composite comprising a polymer matrix having free volume therein and an oxygen scavenger disposed in the free volume of the polymer matrix. Composites whose free volumes contain both macromolecular networks (e.g., halopolymer macromolecular networks) and oxygen scavengers are also contemplated.
Further details pertaining to the making and using of composites are set forth in U.S. Pat. No. 5,977,241 to Koloski et al. and International Patent Application Publication No. WO 98/37964 to Koloski et al., which are hereby incorporated by reference.